The present invention relates to a knitting machine with stitch retention sinkers.
As known, in both rectilinear and circular knitting machines with one or two needle holders, during some particular knitting it is necessary to discontinue the traction to which the already-formed stitch is normally subjected by means of appropriate devices which are generally located below the needle work area.
During such knitting, since the traction normally applied to the stitch is missing, it is necessary to prevent the last formed loops from interfering with the working needles in order to obtain defect-free knitting.
Sinkers which are interposed between the needles and are actuated so as to compensate the lack of traction of the stitch are used for this purpose.
Double-needle holder knitting machines are known which are equipped with sinkers, interposed between the needles of the two needle holders, and in which the sinkers applied to one needle holder are arranged facing the sinkers applied to the other needle holder.
Each sinker is pivoted with one of its portions to the related needle holder, and its end which is nearest to the tip of the related needle has a recess which defines a protuberance which, by exploiting the oscillation of the sinker about its axis of pivoting to the needle holder, can engage the thread hooked by the needles.
Each sinker furthermore has a head which can be rested, again by exploiting the oscillability of the sinker, against the head of the sinker on the other needle holder, so as to provide a bridge between the two needle holders which prevents the already-formed knitting from returning toward the needles.
However, though the known sinkers significantly improve the quality of knittings performed in the absence of traction of the stitch, said known types of sinker have some disadvantages.
More particularly, when the knitting involves only one needle holder, two adjacent sinkers arranged on the same needle holder laterally to a same needle on the opposite sides thereof act with their protuberance on the portion of thread which joins the loops being formed on contiguous needles and astride which the previously formed loops extend.
Due to this fact, it can occur in any case that in the absence of traction of the stitch the previously formed loops can return above the tip of the needle and be engaged thereby during the forming of a subsequent loop, thus causing the undesirable forming of held stitches.
The fact of individually pivoting the sinkers to the needle holder of the machine is furthermore difficult to provide and requires relatively long times.